Huge Oil Tanker Spill in East China Sea Stirs Environmental Fears

HONG KONG — A blazing Iranian tanker that sank in the East China Sea, producing a 10-mile-long oil slick, is drawing concern from environmentalists about the threat to sea and bird life in the waterway.

The tanker, the Sanchi, was carrying 136,000 tons of highly flammable fuel oil when it crashed into a freighter on Jan. 6. On Sunday, the Sanchi sank after a huge blast sent up a great plume of black smoke and set the surface of the water on fire, China Central Television said.

The bodies of three crew members have been recovered, and the remaining 29 were presumed dead, the Iranian government said.

One concern is that the sinking of the ship will pose more of a danger to marine life as the fuel oil it carried spreads instead of burning off. And experts are further concerned that the even dirtier bunker fuel powering the tanker will be released into the sea, exposing delicate marine life to the extremely toxic substance.

Greenpeace expressed alarm about the threat to the marine ecosystem in the East China Sea, which is one of the world’s most heavily trafficked waterways, saying the disaster occurred in “an important spawning ground” for fish.

“At this time of year the area is used as wintering ground by common edible species such as hairtail, yellow croaker, chub mackerel and blue crab,” Greenpeace said. “The area is also on the migratory pathway of many marine mammals, such as humpback whale, right whale and gray whale.”

The tanker was carrying one million barrels of condensate, an extremely light crude oil, to South Korea when it collided with the freighter. When spilled, the condensate can produce a deep underwater plume damaging to marine life.

The Japanese Coast Guard said the fire on the surface of the sea was extinguished early Monday. It said patrol boats were making progress containing the spill, which was reported to be eight miles long and seven miles wide on Monday. Strong winds were pushing the spill toward Japan, away from China.

The Sanchi disaster is the largest tanker spill since 1991, when an unexplained detonation caused the ABT tanker to leak 260,000 tons of oil off the coast of Angola.

Rick Steiner, a marine conservation specialist formerly with the University of Alaska, told The Associated Press that 60,000 to 90,000 tons was likely to have spilled into the sea, calling it “enormous” and “as large as the official estimate of the Exxon Valdez disaster” off the coast of Alaska in 1989. He also suggested that the Chinese government was likely to be understating the magnitude of the spill.

The deaths of the Sanchi crew members prompted Iran’s government to declare a day of national mourning on Monday to honor “the brave mariners who died in the course of their mission.”

Eshaq Jahangiri, Iran’s first vice president, said that efforts to recover the bodies of 29 crew members ceased when the tanker sank off the China’s coast on Sunday.

Because of the release of toxic gases after the explosion, there was little hope that the crew members survived, but efforts to recover their bodies had continued, Mr. Jahangiri said. “Unfortunately, the ship sank and we could not access their bodies.”